Angela Jain, head of the Big Brother commissioning team, said: "The word nigger is clearly racially offensive and there was no justification for its use."

She added: "She [Emily] understands why her involvement has come to an end and she very much regrets what she said.

"I think people watching the show tonight will agree that Emily spoke carelessly rather than maliciously - certainly Charley and Nicky, the two housemates most directly involved in the conversation with her, seemed to accept that she did."

'Clearly offensive'

Ms Jain said that the decision had been taken in the wake of the alleged racist bullying of Bollywood star Shilpa Shetty on Celebrity Big Brother earlier this year.

Shetty, at the International Indian Film Academy awards in Sheffield, said: "Intolerance of any form has to be debunked. For a change [Channel 4] has done some good."

The broadcaster was censured by media watchdog Ofcom and ordered to make a series of on-air apologies for the incident, which prompted more than 40,000 complaints.

The housemates learned the news from a statement left by Big Brother

Labour MP Keith Vaz said: "After the Ofcom decision I thought Channel 4 had learnt all the lessons it was possible to learn.

"But I'm afraid they haven't and there's more to be looked at in this whole sorry episode," he added.

A spokesman for the Commission For Racial Equality said: "Whichever way you look at it, the 'n' word is clearly offensive.

The organisation backed the decision to screen the word, saying "people will be able to see with their own eyes that this is a problem that affects real people".

But a spokesman for broadcasting pressure group Mediawatch said: "They shouldn't broadcast any material which is racially offensive," adding that it would undermine the show.